I am thinking an 8 player map, with the desert tile set, T-1 start, Advanced bases, against one or two AIs set to hard, also with advanced bases(preferably with a NP or collective HQ, to differentiate things).
5-6 of the other player slots are occupied by 5-6 scavenger bases (all scavengers Allied), once again set to "hard" (such that they get free money to make units), as well as outposts all over the place (occupying all oil).

Basically, like the back to basics challenge, but with a much larger and threatening "scavenger infestation"

I loved those Alpha mission maps after getting medium bodies, where the scavengers became an annoyance, rather than a threat.... I only wish scavengers had cropped up in the other campaigns - like a base in a corner opposite the main objective, or some small enclave hiding from Nexus/the collective - presumably those factions wouldn't be as friendly to scavengers (they are not "part of the machine", or are "weak flesh things")

"There is no greater Void than the one between your ears." - Void Ray, StarCraft 2.
Especially the Void between the ears of people who think that No VTOL is a good idea, and won't lead to arty wars. I've won one, and I have to say: I hated it.